Trapezoid Midsegment Calculator — Median Line of a Trapezoid
The midsegment (median) of a trapezoid is the line segment connecting the midpoints of the two legs. It equals the average of the two parallel bases and is parallel to them both.
Solve for
Median line connecting the midpoints of the legs: m = (a + b) / 2
- 1
Sum of the two bases
a + b = 6 + 10 = 16 - 2
Midsegment m = (a + b) ÷ 2
16 ÷ 2 = 8
How does this calculator work?
The midsegment of a trapezoid connects the midpoints of the legs. m = (a+b)/2. Given m and one base, the other base is b = 2m−a. Area = m × h. The midsegment is always parallel to both bases and equals their arithmetic mean.
Formula
How this is calculated
The midsegment theorem for trapezoids states that the segment joining the midpoints of the two non-parallel sides (legs) is parallel to both bases and has a length equal to the arithmetic mean of the bases: m = (a + b) / 2. This is analogous to the triangle midsegment theorem, where the midline of a triangle is half the base.
The midsegment has two practical uses. First, if you know both bases, m = (a + b) / 2 gives the midsegment directly. Second, because the midsegment divides the trapezoid into two smaller trapezoids, and knowing m and any one base lets you recover the other: b = 2m − a. Third, the area formula A = (a + b) / 2 × h can be rewritten A = m × h — the trapezoid area equals the midsegment times the height, which mirrors the rectangle area formula and can be easier to memorise.
All three uses are covered by this calculator via the "Solve for" selector.
Frequently asked questions
It is the line segment that connects the midpoints of the two non-parallel sides (legs). It is parallel to both bases and its length equals the average of the two base lengths: m = (a + b) / 2.
A trapezoid can be split into two triangles by a diagonal. The midsegment of each triangle is half the opposite base. Combining both gives the trapezoid midsegment equal to the average of both bases — exactly m = (a + b) / 2.
Yes — the area formula simplifies to A = m × h, where h is the perpendicular height. If you know m and h you do not need the individual bases, which makes this form convenient when the midsegment is directly measurable.
Also known as
TG we-Calculate Editorial Team. (2026). Trapezoid Midsegment Calculator — Median Line of a Trapezoid [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/trapezoid-midsegment-calculator
TG we-Calculate Editorial Team. "Trapezoid Midsegment Calculator — Median Line of a Trapezoid." TG we-Calculate. 2026. https://we-calculate.com/calculator/trapezoid-midsegment-calculator.
TG we-Calculate Editorial Team, "Trapezoid Midsegment Calculator — Median Line of a Trapezoid," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/trapezoid-midsegment-calculator
@misc{wecalculate_trapezoid_midsegment_calculator, title = {Trapezoid Midsegment Calculator — Median Line of a Trapezoid}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/trapezoid-midsegment-calculator}}, year = {2026}, note = {TG we-Calculate} }
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